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    <title>10.层级选择器</title>
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<body>

    <div class="box">
        <div class="box-header">
            <h1>xxx 管理系统</h1>

        </div>
        <div class="box-main">
            <div class="box-main-left">
                <ul>
                    <li>学生管理
                   
                    </li>
                    <li>老师管理</li>
                </ul>

            </div>
            <div class="box-main-right">
                  <div class="a"></div>
                  <div class="b"></div>
            </div>
        </div>
        <div class="box-footer">
           版权归xxxx所有
        </div>
      

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